Submersible pumping systems are often used in hydrocarbon producing wells for pumping fluids from within the well bore to the surface. These fluids are generally liquids and include produced liquid hydrocarbon as well as water. One type of system employs an electrical submersible pump (ESP). ESP's are typically disposed at the end of a length of production tubing and have an electrically powered motor. Often, electrical power may be supplied to the pump motor via cable strapped to the exterior of the production tubing. Another system uses progressing cavity pumps (PCP), which are positive displacement pumps that consist of a helical steel rotor inside a synthetic elastomer stator bonded to a steel tube. As the rotor turns within the stator, fluid moves through the pump from cavity to cavity. The resulting pumping action increases the pressure of the fluid, allowing production to the surface.
One technique involves suspending an electrical motor on a string of production tubing in the well. A progressing cavity pump is lowered through the production tubing and stabs into engagement with the previously installed motor. A line, which may be a wireline, is used to lower the pump through the production tubing is retrieved. Supplying power to the motor rotates the rotor of the pump, which pumps well fluid out the upper end of the pump into the production tubing.
While this technique works fine in many wells, in some wells, debris in the well fluid can settle out and drift down onto the pump, eventually hampering flow. For example, in coal bed methane producing wells, the pump is employed for dewatering, and the gas flows up the annulus surrounding the production tubing. Coal fines are typically entrained in the water and tend to accumulate. This accumulation requires subsequent cleanout.